Etiology of breast development in the BCERC network: role of socioeconomic status Dejana Braithwaite, Robert A. Hiatt and BCERC Investigators Abstract This application is concerned with the role of socioeconomic status (SES) and race/ethnicity in the timing of breast development and menarche as an early life marker of breast cancer risk. Secular trends toward earlier age at the onset of breast development and menarche have spurred the creation of the Breast Cancer and the Environment Research Centers (BCERC). It has been established that African American and Hispanic girls mature earlier than their white counterparts but the reasons for this biologic change remain poorly understood. Currently, there are major information gaps on the determinants of pubertal onset among minorities. We hypothesize that social and economic factors may reflect upstream determinants of early puberty. In the network of three prospective multiethnic cohorts of girls (n=1,238) aged 6 to 8 years at baseline and actively followed for 4 years to date at three sites in the United States as part of the BCERC, we will determine whether previously unexplored socioeconomic factors (household income, parental educational attainment, home ownership, residential crowding, wealth) can explain some of the variation in the timing of pubertal outcomes across and within racial/ethnic groups. Our specific aims are to determine the nature and strength of the association between a wide array of SES indicators and pubertal onset (AIM 1) and whether socioeconomic factors modify the association between race/ethnicity and pubertal onset (AIM 2). The large sample size of the BCERC network, including the data already collected via extensive longitudinal assessments of a comprehensive array of chemical, physical, anthropometric, social and genetic factors in addition to serial exams of pubertal development make it a unique resource. Major strengths of the study are: 1) The hypothesis that socioeconomic status may play a role in pubertal onset has not been systematically explored;2) Combining data from the three BCERC centers will improve external validity, making the findings more generalizable to all girls in the United States;3) The cohorts have a substantial proportion of girls from low socioeconomic and minority backgrounds;4) Large sample size, longitudinal design, detailed and accurately measured data, high retention rates and innovative hypotheses represent a much needed advance over existing research;5) innovative statistical techniques such as CART have not been previously employed in the present area of research. The Small Grants in Cancer Epidemiology Program mechanism provides an ideal vehicle to accomplish the objective of this study, which is aligned with the NCI's mission to determine the underlying causes of cancer health disparities. PUBLIC HEALTH RELEVANCE: Narrative This application is concerned with the role of socioeconomic status (SES) and race/ethnicity in the timing of breast development and menarche as an early life marker of breast cancer risk. The decline in age at the onset of breast development and menarche that has been observed over the last few decades among girls in the United States is a major public health concern. These developments have spurred the creation of the Breast Cancer and the Environment Research Centers (BCERC). It has been established that African American and Hispanic girls mature earlier than their white counterparts but the reasons for this biologic change remain poorly understood. The possibility that social and economic factors may reflect upstream determinants of early puberty and account for racial/ethnic differences in this outcome has not been systematically evaluated. In the network of three prospective multiethnic cohorts of girls (n=1,238) aged 6 to 8 years at baseline and actively followed for 4 years to date at three sites in the United States as part of the BCERC, we will determine whether previously unexplored socioeconomic factors (household income, parental educational attainment, home ownership, residential crowding, wealth) can explain some of the variation in the timing of pubertal outcomes across and within racial/ethnic groups. To accomplish the goals of this project, we will: 1 Determine the nature and strength of the association between socioeconomic factors and pubertal onset (AIM 1) 2 Determine whether socioeconomic factors modify the association between race/ethnicity and pubertal onset (AIM 2). The large sample size of the BCERC network, including the data already collected via extensive longitudinal assessments of a comprehensive array of chemical, physical, anthropometric, social and genetic factors in addition to serial exams of pubertal development make it a unique resource. Major strengths of the study are: 1) The possibility that socioeconomic status may play a role in pubertal onset has not been systematically explored;2) Combining data from the three BCERC centers will improve making the findings more generalizable to all girls in the United States;3) The cohorts have a substantial proportion of girls from low socioeconomic and minority backgrounds;and 4) Large sample size, detailed and accurately measured data, high retention rates and innovative hypotheses represent a much needed advance over existing research. The Small Grants in Cancer Epidemiology Program mechanism provides an ideal vehicle to accomplish the objective of this study, which is aligned with the NCI's mission to determine the underlying causes of cancer health disparities.